Many data centers are typically cooled by operation of one or more different types of air conditioning units. Primarily, Computer Room Air Conditioning (CRAC) units and water-based cooling distribution units (CDU) perform the majority of the cooling needs. However, a substantial percentage of existing data centers will have insufficient power and cooling capacity in the near future. Even if this increasing need is met, power is one of the highest operating costs (after labor) in the majority of all data centers. Moreover, data centers are responsible for the emission of tens of million of metric tons of carbon dioxide emissions annually.
A data center may be defined as a location that houses numerous IT devices that contain printed circuit (PC) board electronic systems arranged in a number of racks. A standard rack may be configured to house a number of PC boards, e.g., about forty boards. The PC boards typically include a number of components, e.g., processors, micro-controllers, high-speed video cards, memories, semiconductor devices, and the like, that emanate relatively significant amounts of heat during operation. For example, a typical PC board comprising multiple microprocessors may consume approximately 250 W of power. Thus, a rack containing forty PC boards of this type may consume approximately 10 KW of power.
The power required to dissipate the heat produced by the components in the racks is generally equal to about 30 percent of the power needed to operate the components. However, the power required to dissipate the heat produced by a plurality of racks in a data center is equal to about 50 percent of the power needed to operate the components in the racks. The disparity in the amount of power required to dissipate the various heat loads between racks and data centers stems from, for example, the additional thermodynamic work needed in the data center to cool the air. In one respect, racks are typically cooled with fans that operate to move cooling fluid, e.g., air, across the heat emanating components; whereas, data centers often implement reverse power cycles to cool heated return air. In addition, various cooling mechanisms have different cooling efficiencies. For example, water-cooling units operate more efficiently than air-cooling units, but are costlier to install. The additional work required to achieve the temperature reduction, in addition to the work associated with moving the cooling fluid in the data center and the condenser, often add up to the 50 percent power requirement. As such, the cooling of data centers presents problems in addition to those faced with the cooling of racks.